The 25-year-old forward joined Latics from St Mirren minutes before the January transfer deadline on a wave of expectancy.
But he made only four appearances - including one league start - in the second half of the campaign, with his absence a regular source of confusion from sections of the Latics fanbase.
But his spell on the sidelines has only doubled the Irishman's determination to hit the ground running when the players report back at the end of this month.
"The plan was to take maybe one or two weeks off, and then come back early and try to be fit as I've ever been for the new season," he said.
"I'm aiming to hit the ground running as best as I can in pre-season, and hopefully try and smash it next season.
"Obviously it was hard coming into a club and a team that was top of the league, the boys were in top form.
"I managed to get a few opportunities, and hopefully I'll be able to get a few more next season and take them when they come my way.
"Hopefully I'll be able to show the fans a bit more of what I've half shown so far."
Off the field, McGrath certainly has no complaints with his lot.
"The lads have been brilliant so far, since I came in, really making me feel at home," he said.
"It's a great group, you can see that with what's happened on the pitch, and we fully deserved to win the title.
"We maybe could have wrapped it up a little earlier than we did. But the gaffer said all along it would go down to the wire, and he proved to be right."
Latics are still basking in the glow of their promotion, which has set up a return to the Championship after two years in League One.
For McGrath, it represents a massive opportunity to showcase his skills at a level he believes is one of the best on the continent.
"The main reason for coming down here was to play in the Championship, and thankfully we're there now," he added.
"As a player you want to play in as high a division as you possibly can.
"Obviously the Premier League is the pinnacle, but the Championship is also one of the best leagues in Europe in its own right.
"You can see the quality of the players and teams from top to bottom, there's some massive names in there who are all fighting to reach the Premier League.
"That's where you want to be, and hopefully we can find our feet quickly and give a good account of ourselves.
"Even in League One, there were some quality teams and players in there, and for us to win promotion - never mind finish as champions - was a fantastic effort.
"Considering where this club was not too long ago, it's been an unbelievable effort from everyone concerned, and the next step now is to kick on at a higher level."